Thermodynamic and kinetic considerations for biodiesel production by reactive distillation

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Reactive distillation (RD) methods have only lately been introduced into biodiesel (BD) production. They offer several advantages that could benefit the efficiency and drop production costs. A bench-scale RD unit was built, and results obtained are interpreted from kinetic and thermodynamic perspectives. Analysis of samples taken from the prereactor and the reboiler product was achieved by a conversion-viscosity chart developed that returned BD conversion from the measured viscosity. It was found that 50–60% conversion was possible at ambient temperatures, with stoichiometric feed ratio and a stirrer. Thermodynamically, Raoult's law was used to predict the vapor and liquid composition in the reboiler. Three different scenarios were set up with different feed molar ratios. It was found that despite the large difference in boiling point temperatures, separation of methanol from the reactant and products mix was limited. Under all modeled scenarios reported, an appreciable amount of methanol would be lost to the product stream. The affinity of the methanol to remain in solution was greater than expected, based on the boiling points, and only when appreciable amounts of methanol were in solution could larger amounts of methanol be removed. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 373-376, 2013